Bsheets-sheei



SPEED H. N. HURD.

CONTROLLING SYSTEM FOR MOTORS AND THE LIKE.

APPLICATION HLEO mm H. 1919.

Pafenwd Oct. 10, 1921 B SHEETS-SHEE1 L HUGH N.HURD $4 hills mtolmdq H.N. HURU.

SPEED CONIROLUNG SYSTEM FOR MOTORS AND WE LIKE. APPUCAHON FILED mu14.:919.

1 ,431,733. Patent/8d Oct 10, 1922 B SHEETS-SHE 2.

H. N. HUHU.

SPEED CONTROLLING SYSTEM FOR MOTORS AND THE LIKE.

I APPLICATION "LED IULY 1 5X9. 1,431,733. Patented Oct. 10, 1922.

H SHEETS-SHEE 3.

awmMo'r, HUGH N. HuRu $45 Ms fitter/nu,

mkd/fla zz uw H. N. HURIL.

ROLLiNG SYSTEM FOR MOTUHS AND THE LIKE APPUCATIGN FILED mm 14. \919.

SPEED CONT 8 SHEETS-SHEET 4.

1 H .fl. T 0

R E E lwwwto'z 40 HUGH N.HURD

$4, ms Gum-m,

H. N. HURD. SPEED CONTHOLLINGSYSTEM FOR MOTORS AND THE UKE.

APPLICAHON HLED IULY l4, I919. 1,431,733. Patented 00a 10,1922.

8 SHEETS-SHEET 5.

amvamfom HUGH HURD 3513 his atta n/Lew H. N. HURU.

SPEED CONTROLLING SYSTEM FOR MOTORS AND THE LIKE.

APPLICATION FILED IBM 14, I919.

Patented Oct 10, 1922.

B SHEETSSHEET 6 H. N: HURD. SPEED CONTROLLING SYSTEM FOR MOTORS AND THELIKE. APPLICATION HUID )ULY 1!.1919. 1,431,733. Patented Oct 10,1922.

8 SHEETS-5HU 7.

avvuau-to c HUGH N. HURD H. N. HURD.

SPEED CONTROLLING SYSTEM FOR MOTORS AND THE UKE. APPLICATlON HLu) luv14. \911.

1,431,733. Patented Oct. 10, 1922.

B SHEETS-SHEET 8.

\numumma nunmummumuw umm *ummmmnmu Elwuewtom HUGH HURD 32213 111113SttOT'M/Qla and further my permits of a ch durin the rolli [n t eapplica invention as a p l desirably emp trolling meens f0 ers orfootois energii or differential ele controlling circui spective prime rnpendent prime tors directly connectedt d apparatus and suitables'm he'mounted npon the shnf ""otorsj, .th'etl tmi bet'weh cuits ma ybeemployed trdllin driv to tron of the referred em i d tr llin meansillustratin e modified arrangement wherein ange in ratio being efl'ectodthe centre ling motor is driven by an indeg operation if required.

pri ciples of my elated therewith and arranged to be operabodimentthereof tively responsive to the controlling circuit. y electricallyoperated con- Fig. 3 is a die rammetic view illustrat.

e reipective-pzihze'mqvin'g'a fiurth er m ificetion inthe operating dropmeans for the controllm esbetwcen a Continuously operating motor isemployed rheosta't 'w'herein ts fiss'ociated with the refcrjedjuscuigithe flieo'stat. 7 5

vers pesirab g means ,the con ngen'ient, of this ch tive to actiinte eQrheo ile its iifo r'es y. 1

ective geiira'tbrlbltinodified arrangement wherein COHCIOlllDQ tbenergize'thecotirheostats are associeted with each of the sins in an drivin motors and operative in inverse re- D operal'ation; y meens ofthecontrolling circuit. stat 'for i-eg a g a '-Fig.'6 is adi'egremm'etic view indicating circ'uit'of the moltor'to th'ein'anner'in ivhich unbalanced fluid resei'd iij iiiip'rovedinetliodto-regulate one of the 'prime movers so as nipl'oyment of di adult'zible 't ell my invention speeds of the motors and connected and verious'ty f to ope'rete thecoliii cfiling rheostat in clifi'erqvli ize t iseeuaentlalrmannr.

proper seqiiehe 8 illiist'i at s' entarrangement of my I the Fl Qisediagramnmtic view of a further may-he" ecti-icino-mod cationwhereizi-the'-operation of the 'verollsor other controlling rheostat isarranged to be re lge'neratdrs'iimy s'pofi'sivtdc'iiiiiigs 0r ariationsin the t of each of the value of the controlling circuit. 30 he of po-Fig. 5 is a similar view illustrating a sures may, insimilar manner heemp oyed fl'gi-rbfitial o restore the 'baliince or predetermined h90 toritio.

ed ratio Fig. 7 illustrtesh further modified em- "Lforthe'd riving ofbodiment of myinvention wherein governor 1 be understood that this means'are arr'an thod of ged to be responsive to the operation tip d r'atiotheir-obi? ii 1 ventioi1}'wh{erein a differential controlling,

tween. Furthermore, in" we ee iee er. soureesofenergy of er 1y m i speed1'' are applied to the, devices in the several h? 1 is a tour carriedand arranged \vhereb en i h teb w enntrqlling'means peratiqn oione'eother. p is a siinflar diagrammatic view closed the operating circuitsare of unlike trical o0 latethe with Fig. 2

either electricel es rfei'ii tionvvith fl draulic or air differentialp'r 't'mm e P e ver ab e}. o o era he d ugfibed P vanfq by re erence toth wherein there" suitable emhodim l ciples and'wherein like 5 new d a'g f view of n de spectively of in tf of my inventiomwherewhich actuallyused Id 'pressur where .jin

ants .of

y' the res no e es'siire' is instrumentiilin roperritio t1on. p p endotherfe'etures 1nd 'edinstallationjof'my improved method I haveunderstood controlled .theloperation of a motor drivin inven e -acco ii1m shown. 511

g psi ts or which operhte 'in's'uccessi connected to 'regutions in'the'ener 'circuit is Iemploy'edto effect the closing and with openm Y ofan' hdlitional circuit or su lesmtablchii'racfer .fi ntary s pp ource ofenergy.

or Ref e rrmg'to'tlie drevnngs in Fig. 1 there l1 is illus treted d ia.remmstlca y a. n n. proved themstglht on empo'ying the princip es and Iain' eeture's'o'finy invention in an arrangement iqthe speed of thewh1ch I have successfully reduced topracut the en ire tice'm'the drivingof successive pairs of rolls, lidaptedjior rolling steelbars. In thisthe so-cslled sizing rolls with relation'to thii prmrolls so es,toflmauntain a predetermined reiei'enoe numerals speed. mm between therespective rolls on upon the bar. In the srrangen'ient of Fig. 1 asshown A and'B aie the (prime 'movers consisting reependent electricmotors, of

A is driven by an positive motor shgfts' latter liming connected todrive the sizing [the dilfere'ride ofl 0- roll Stand? or last piss inthe rolling opera will.

of employ in; varin piles of the respective prime of theprime moversmovers or motors- A: and B to restore the proper ratio therebetween,where as'disto hand. adjustment to character. there is associated witheach of the motors A and B a small d. c, generator and l). in thearrangement as disclosed the iii-matures of generators C and D aredesirably mounted directly on or connected to the armature shalts of themotor A and B respectively.

in accordance with my invention it is arranged that any dillerenee inpotential be tween the circuits of the respective generators C and Dwill operate through a controlling circuit 4 to energize controllingmeans operative to regulate one of the main driving motors, as hereshown the motor The controlling circuit may be connected to the positiveor ngipative sides of the generator as desired. l eans may desirablyregulate motor B by adjusting the value of a resistance in its fieldexciting circuit which may be accomplished as here disclosed by means ofti rheostat it in series with the field exciting circuit of the motor Bas shown. be controlling arm 0 may desirably be moved in one directionor the other to vary the resistance under control of a small motor Ewhich is energized by the controlling circuit and is ma e responsive toany dillerences in potential between the aforesaid generator-s C and D.

The operating connections between the controlling motor E and therheostat adjusting arm may consist of any suitable connections and thecontrolling motor B may desirably be of a reversing type, whereby therotation of its armature in one direction or the other. depending uponthe direction of current ow in the controlling circuit, will transmitits motion to the rheostH-t arm 50 as to increase or ecrease theresistance in the field excitation of the motor B.

The generators and D are oia type which under normal conditions willvary in their voltageoutput only rtion with changes of speed or inresponse determine therelative to be maintained. In thc arrangementdisclosed the field circuits of the motors A B and E and also of thegenerator C and D are all separately excited. However, the. fieldexciting coils o generators C and D and of the motor E gin-d from the.same circuit 5 so that'there will he no variation in the relativeoperation of these res by reason of diftive devices tering fluctuationsin their fields. Atr, 1 adjustable rethere are indicated suitableheostats in series with the field coils of the respective generators Cand D lw thiadjustment of which the ratio of iii-Id tins of thegenerators C and D relative in each other may be regulated and inconrnutntt the speed ratio determined;

lu the operation of the system as descril tti it will he understood thatthe motors speed ratio direct 'pro- A and ii. which may he ns 't' lnrime movers. may be widely separated lll liicir relative locations andmay be driven by independent electrical sources of po er. They are thussubject to variation in their operation in response to variations intheir energizing circuits and also under variations of load reactions.Under normal conditions upon the rotation of the armatnres of the motorsA and B in their predetermined speed ratio, it is designed that thegenerators C and D shall produce electrical currents of like value sothat there shall be balanced potential energies and in consequence nocurrent. (low in the controllin circuit 4. As will be further understood51c relative speeds of the driving armatures of the motors A and B toeffect the generation of balanced ener- ,qies is determined by theadjustment of the field resistance r of the generators C and D. Theratio thus established thereafter will be maintained automaticallythrough the action of the controlling means or rheostat R. In sooperating it will be understood that the controlling means will be soconnected that upon bein energized by a flow of current in one directionor the other it will operate the rheostat R to govern or regulate themotor B in a manner to compensate for any disturbance in the s d ratioof the drivin -armatures. This effect is 'accom 'plishe by introducingadditional resistance in the exciting field of the re ulated motor Bwhen the armature thereo tends to decrease itsor to cut out resistanceproportiopate to any tendency to increase its "speed with relation tothe armature of fr'o'm' tha'tpf the-predetermined ratio.

In's'o' maintaining the balanced-speed relation between 'the armature ofmotors A and -B,"thje controlling means-as aforesaid 'willbo responsiveto any ditierences in the otential values of the generator circuitsand"will'-be"-instantaneous in its action to I restore thepro 1'relative speed ratio irre' spective of variations in the s eedoi opera--'t1o'n. 'Ii1-other wordsthe constant relative "speed-of the respectivemotors will be main tained-throughout-the entire ran e of operatingspeeds under varying eon itions of loador of rise and fall in the wer.The arran merit as descri thereby employs the un ilanced energies torestore the balance of the independent prime movers by the egulation orgoverning of the one with relation to the other so as to compo anydisturbance of the determined ratio caused by variations in the rotaryspeed of one or the other of the prime movers whether such variation iscaused by rise and fall of the driving forces, change of field go ofarmature shunt or change of speed under varying load conditions to whichone'or the other of said prime mo is subjected.

connection with Fig. 1 -a Thompson balance arranged To more specificallydefine-the operation of my improved method of control it will beassumedlIl the first instance that the be notiow of current in the mntrollingor there will be a-slowing .u and'accordingly there xvii be-a-flow-ofcurrent from the generator C of the motor A resulting from itsrelatively increased speed with respect to the generatoriD. .The efl'ectthereofwill be to operate themotor E to transmita rotaryefi'onhto therheostatarm of the controlling to'increase the resistance in theexciting -:field of the motor B. As a result the rotary efl'ort of-thelatterzmotor "will be built up orl increaseddocompensate for thevariation -in load and; to. restore and maintain the pror relativespeeds.

Vfiiile -I have shown and described -in desirable arrangement or. systememploying-the features of 'll'lj' lll-GSOlllPl-HVGHlBlOII it.w11l beunderstood that the same is-subject to ya rious modifications withoutdepartin,g;from the substance obmyinvtention. ly-Lhave illustra '-in-Eig. i2 a suitah le modification :ivhereinthe-eontrolling motor-iE,connected to the regulating rheostat R, is arranged to be operatedbytthe current of an-inde energizing circuit 1.0,tlh01l8-tb8f circuitbeing arran ed to be closed by means oi asuitable pole' ianger -Panran'gedto-be actuated -'by a relay circuit 11 associated-withaTl1ompson balance circuit closer Tarrang responsive to .the controllingor differential circuit 4. In this arrangement as indicated, 12, 12indicate the stationary coils of the in series with a shunt-circuit 13connected to the exciting circuit 5. 14, 14 indicate the movable coilsof the-Thompson balance carried by a pivtacts carried by the arm 16 andadapted to close the circuit ll by engagement with terminalslB r 19whereby circuit 11 is closed either through branch 20 or branch 21 forenergizing magnets '22, 22 or magnets 23, 23 respectively. The magnets22 when ener B-are each directly I connected to drive rolls andthat therheoe respective stands rheostat R in a direction .lrangement is shownotinuously driven :motor -ture mounted uponuand rotating a drive 105ndent edtobe gized will close contacts 24, 24 to close the circuit 10 to(1b be understood .the resultbe that ulpon the opera mg operation willgenerators Cand CJOILOE the be unener 'zed. A variation in the E willrotating speeds o the generators C and D from that of=the predeterminedspeed ratio will,:as hereinbefore described, cause a current flow in thecontrolling circuit 4, the direction of which will determinethe movementof the switch arm 1.6 to close :the cirmotor circuit E devices shown. Aswill -be understood the driving motors A and B may be of similarcharacter, either a. c. or -d. '0. type, or may .95 be energized byunlike circuits desired.

erators and-motors maybe of either .a. c. or .d. 0. type as may .bedesired.

'In' .ig. 3 a further suitable modified arherein the motion for --arm ofthe rheostat e endently and can aving its armamoving the oontrollinlsderived from anin shaft 28 upon whiohi are a bevel gear 33 en- 11ogear 34 to which the the controlling rheojwcent .to eachof the gaging acooperating controlling arm 35 of stat R is aflixed.

In this arrangement for operating the rheostat the controllln This may.be effected in any esirable manner, for instance through theinstrumentality of a Thompson balance as described or similar deviceadapted to close a circuit through one or i the other of contacts 36 and37 to energize traction magnets 38 or 39 suitably connected to theshiftahle coupler elements 36 and 37 ICS1)lL'tl\'Cl From the foregoingarrangement it will result that upon the closing of the circuits througheither of the magnets 3 or Jl.) depending upon the direction of thecontrolling or differential circuit r the motor (r will be coupled up totransmit its motion to the controlling arm of the rheostat in onedirection or the other. so as to increase or diminsh the resistancevalue of the exciting field of the regulated motor.

While as hereiubefore described in my improved system of control itmaypreferably he arranged that the controlling meansshall be operated inres onse to reversals of the flow of current in t e controlling circuit4 it will be obvious that the operating motor or the regulating rheostatmay be made responsive to changes or variations in the ralue of thecontrolling circuit 4, so as to correspondingly adjust=the rheostat. Anarrangement of this character is shown diagrammatically in Fi 4 whereinthe arrangement is general y similar to that of Fig. l but wherein, asmechanical means such asaweight 40 carried by a drum ll rotatablyconnected to the rheostat arm is employed to be normally operative tomove the rheostat arm in one direction.- The voltage output of thegenerators C and D are ted by the rheostats r-to establish a normalcurrmt flow in the oontrollin r circuit 4 to energize the controllingmotor to produce a rotary efiort in the opfrom that transmitted by theweight -10 and of a value under normal conditions to balance the effectof the weight 40. Thus upon the rotations of the respective drivingmotors A and B in.their predetermined speed ratio a normal or'balancingcurrent flow will be established in the controlling circuit 4 with theresult that the rheostat arm will remain stationary and any increase ordecrease in the normal'current flow in the controlling circuit 4 willcreate an unbalanced relation between the rotary efl'orts of thecontrolling motor E and the weight 40 resultingin a correcting movementof the rheostat arm in response to the unbalanced effort.

Also while I have illustrated in the hereinbefore described applicationsof my invention an arrangement wherein the controllin means is operativeto maintain a fixed spe ratio by regulating the driving forces orenergies of one of the motors only. it will be understood that thecontrolling means could be so arranged and connecte to have a regulatingeffect upon both of the driving motors and in inverse relation. y way ofillustration 1 have illustrated diagrammatically in Fig. 5 anapplication of my invention adapted to be so operative. A desirablemanner of effecting my improved control by the regulation of both of thedriving motors 8 Bin as illustrated consists in the association of a.second regulating rheostat 45 with the con trolling motor E in additionto the rheostat an installation generally similar to that of Fig. l. Therheostat arms of the respective rheostats R and 45 are connected to bemoved in unison by the motor E under the influence of the controllingcircuit 4 and the rheostat R as heretofore described is connected tointerpose resistance in the field exciting-coilsof the motor B and therheostat 45 is similarly arranged'in series with the field excitingcircuit 46 of the drivg motor A but reversed in its arrangeact ininverse relation to that of the rheostat R with the result that upon themovement of the rheostat arms in unison the rheostats will actproportionately to increase the resistance in the exciting field of onedriving motor and to de crease theresistance in the field excitincircuit of the other driving motor. It wil l thus'be seen that in theapproved modified form ofmy invention the difi'erential or unbalancedpressures of the controlling circuit 4 will be operative to compensatefor variations in the predetermined speed ratio by the regulation ofboth-of the driving motors through the operation of the adjustingrheostats and 45 connected therewith. :In accordance with furtherfeatures of my-invention I have shown in Fig. 6 a further application ofmy improved principle hot 0 oration for the control of independentriving means or centrifugal -pum s in an arrangementw ereby the dilfer-'entia pressures of the fluid are employed to actuate a controllingmeans of the character described. As diagrammatically shown, 50 and-51mmrotary pum s which may have their motors mounted direttly upon thearmature shafts: of independently controlled driving motorsas will bereadily understood. Each of the pumps is provided .let chamber 52, 52through which the fluid passes in its flow to the outlet passages 54,54'and communicating with each of these chambers 52 there is provided acylinder 55. Within. the cylinders there are pistons 56 movablethereinunder the action of the fluid press res and the respective istons 56 areconnected as here indicate to operate rheostat'arms' 59 of generatorrheostats 60, 60. In the present instance an arrangement is shownwherein the controllin generators C and-D are mounted upon t e armatureshaft of a-constant speed motor 62 and the output of the respectivegenerators C and D are arranged to be proportionate to the operatingspeeds of the driving motors A and B by the regulation of the fieldexciting circuits of the generators. here indicatr ed the rheostats 60,60 are each arranged in series with a field exciting circuit 64 and 65for the respective generators C and D.

6 linen-13s In the resulting operation the'current flow B the movablecontact 71 and 72 under the in the controlling circuit4 wiil be governedaction ofithe governors 68 and 69 will by the differential'output of'therespective asmime corresponding positions with respect generators Glandin resporise to thead to their associated rheostnts. Therefore, un-

ustmentof the rheostat 60, v'vhich as indider theaforcsaid conditionsthe resistances 70 catedwwill-vary the field excitationof the X-l andX-3interp0scd between the positive associated enerators in response toElie-ad main =avnd the respective Contact arms 71 justment'o therheostat controller arms 59 and 72 will be balanced or ofcorrespondunderthecactionof the fluid pressures of ing value 'wherebythere will he no current the m'spectivePumpsfiQaand 5Lactin '-uponflow'in the-differential circuit 4 Upon ra- 75 the pistons 56. Thec'urrehtflow in t d cirriation of-thes'peeds of the motors A and R cuit4is thusdifi'erentiallyproduoedand'refrom that 'o'f-"the predeterminedratio the lated to the'operatingspeedsof-the nespecgovernors 68 and 69will operate the movntivedriving motors A-andB operating the ble"contact arm 71 and 72 to assume unbalpumps 50 and 5L and will energize-the=conanced positions whereby there will be a controlling arm of acontrolling rheostatlR respective-rheostats. In other words whenconnected in'seneswiththe fieldcircuit of the positionof the rheostatcontact arms 71 one of the drivin' motors, as" here shown: the and 72are such that total resistance of the tlierefom'follovi -thabtheportions-X and X ual the total resistfield excitation of the drivingmotor B-will anceof the portions X and X upon oppobeautomaticallyregulated in' response to'tlie site sides of themntactarmstherefrom there differential current flow III-the circuit 4 s0 willbe'no current flow in the controlling ciras to regulate the drivingforcs o'fi tlie inocuit 4; "An'=increese of speed of the drivtor sons tocom nsate for any var-ia- --in'g=motor A 'will be operative to raise thetions fromthe'pze etermined:;speedratio. rheostat'oont-act-arni 71 andcorrespondingmay 'be' operative in los'ponsertodifferential ing'circuitt frbm't'hat side-of the line. In pressures of other impelling forces.for insimilar'mann'ershduld the conhict arm 72 stance steam or air. l rbe raised'with relation to the position of the W-iH bePPI'eciafed-flieufeafiuqes of ai'm"7-1 there="would be'establishedacurrent my'invention and ini roved principles of flow in 't'he 'oppositedirection. The effect operation are suseeptibl e of many and variofi'thodifferential current in the circuit 4 so ous modificationsrwvithoutdepartin from producedw' fll 'be to energize the controlling t e anan'ce"ofithe-invention as d ned in motor E in the manner as heretoforedethe appended claims. Asa fnrtherillust-rasoribedythe'ltter motor beingconnected to tion thereof I-haveshown dia aminirtically'opointeuhe'regulating rheosta't. R arranged in Fig. 7 a further modifiarrangement in sm'iesfivith the field exciting circuit ol for producing"the 1 differential mntrolling o'neof the'driving motors. Thedifferential circuit. As-there indicated centrifugal govcontrollingcircuit 4'is thus made responsive ernors 68 and'69 may operatively contovariations in the relative speeds of the nected to'the respectivedriving motors A drving motors A and B and operates and B so as to be 0erative in proportion through the rheostat- R to compensate thereto thespeeds of he The governors for.

8 an .69 asindicated are suitabl con- In Fig. '8 'I have showndiagrammatically nected" to actuate pivotal arms 71-and 72 of a furthersystem of my invention wherein u rheostats 73.nnd 74. The rheostats73and differential controlling circuit is arranged 4 are conaected'inarallel relation across to effect theregulation of an additional e mainsofa Suits, 1e circuit. The movcircuit or source of energy to supplementa able arms or contacts 71' and72et their'onter Lmain supplycircuit whendesired. The inn ends' contact With'the respective rheosta ts provedarrangementnow to he described is 3 and 74 and are connected attheir'inner particularlv desirable where an outside ends by the w res ofa controlliii' circuit source of p'wer js emploved and where it is t thelatter being thus closed in not or desirable tdfniunt'ain theconsumption of or rheostats 73=and 74 and being adjustable not exceedingapredetermined volume. T0

with regard to'the respective r eostats on he so operative it isarranged that when the der the action of the independently operatedconsumptioh of power or load exceeds the governors 68 and 69. normal thecontrolling circuit will be operhe resultingoperation will be that uponati-ve'tb cbnthol an independent generator or the 'mnmtnimng of theproper relative sourceof electrical energy wherebv thelatter speeds inthe operation of the motors A and will supply the amount/of energysufficient to 13 co'rii' ensate for the peal: of load and upon thefalling oil of the load below normal will he efiective to diminish orcut out the current supply by'the auxiliary circuit and in thenemploy'tlie outside circuit alone to carry the full load. i 'ln theapproved arrangement or system Shown diagrammatically in Fig 8 and Dindicate two generators driven by a con stant Is'peed motor 78 and at T9and there-are shown the field exciting circuits therefor. "The circuits79 and S0 of the gen craters C and D respectively are shown in'sh1int"arrangement with a field exciting c ir'ciiit81. In each of saidfield exciting jcircuitstlie're is shown interposed n suitableadjustable'-resist.anoe. As here shown the'resistances may desirably bethe usual compressible carbon resistance piles 84 and fifr'connectedjinseries with the circuits '79 and 80 respectively.

"It is designed that the resistance 84 shall be 'adjustab e'in responseto the load upon the'to talloa'd circuit or mains 86 and that the"adjustment "of resistance shall be similarly responsive to theload uponan auxiliafy 'or' supplemental supply circuit 88 from an auxiliary orsupplemental generator G which may be driven by any suitable power suchas a turbine 90. The supplemental circuit mains 88 are arranged inparallel relation with supply maiiis 91 from an outside or limitedsource of power. As will hejnnderstood'the current supplied by theoutside-mains 91} whichrriay be termed the limited source 'of powermaybe purchased power 'supplied *under "contract, in connec- 'tion'with' which"it is desir:\hle' not to exceed a predetermined maximumload. The supply mains 91 and supplemental supply mains 88 are connectedwith th total load mains '86 whereby the latter receives its totalcurrent supply from'the circuits 88 and 91 and tllllS from the limitedor outside source f-poweror jointly from said source and from thesupplemental generator =In accordance with my invention it is arrangedthat't-he operation of the supplemental generator shall be responsive tofluctuations in the t tal load or mains S6 with respect to the circuitof the limited source of owcr. This result is accomplished through theinstrumentality of a differential controllin g circuit 4 connected tothe respective contmllinggenerators and D. The current the circuit twillbe established in one direction or the other resulting from anunhalancedrelation in the output of the generators C and D The latter inturn will be variable as aforesaid in response to the respective loadsupon the total load mains 88 and auxiliary circuit 88. To be soresponsive as indicated the iesistance pile 84 is arranged to becompressible under the action regulated "rent' flow in inotheiresistanoe 84 in thereby causing a citation of generator-"D sistaiice'85 -in loads or loads below that of the capacity to effect the cuttingout "outside circuit only of an actuating magnet 92 energized by mainsof series and shunt coils in circuits 93 and 94 connected with the totalload mains 86. In similar, arrangement the resistance 85 is compressibleunder the of a magnet 95 energized by series and shunt coils 96 and 97'connected'to the auxiliary supply mains 88. A controlling motor E. isarranged with its armature in circuit "with the controlling circuit 4whereby the motor B will be actuated in response to the currnt'flow inthe controlling' circuit 4 t'resulting from the unbalanced pressuresbetween the generators C and 1).: The (50 trolling motor E is-oonneeted'to actuatothe controller arm" rheostatRcoiinemd" citing circuit 99' ofthe supplemental gen- 'erator G5 'Thu's the'outpi' t of the latter is inresponsejto the-differential curthe controlling circuit -43 Theresulting 'operation 'is as-follows I with thosystem set forthe' limit-orcapaeity' of power to' be'suppli'ed=by exteron the total load .main86 will vary the: strength of the aerator byaxljust- O the field circuit7 9. he effect thereof'willbo'to unbalance 'the voltage between thegenerators-2011i difierential current flow therebetween. "-The current'flow thus established" will energize the'controlln motor-1E to rotatetho'rheostat coiitroller -arma98 in a direction to chain c thewalue ofthar'rh'eostat R :toregulate t e output'oftho-supple- 1 mental generatorG 56' as-to take-care of or compensate'for the change in load-on themain 86=and leave the demaiidonthe mains 91 constant. '-In-'corresltionding' manner the changesof load on' the su plemental supplycircuit 88 will vary the-vii ue of the field exby adjustingthe reitsfield circuit. In conseuence the voltage output of'generatorgulatedunderchanges of'load on the cir tween the go 'eratorsresponding-l affect trolling motor E. :The rheostat R will therefore beautomatically controlled so that the current supply ofigenerator will beso regulated that it will take care ofthe peak o the" in excess of thecapaci external circuit 91 and will-be'variab e indirect ratio withvariatioiisin'the excess 10a of'thecircuit 91 of thesupplemental action3 '11 al or limited source ofpower or mains 91, a change'of loadproportionately field excitation of the g the action of the 0011-current supply circuit 88 to-then employ theto carry the' full load. Aswill be appreciated the principles of my improved system'inaybe embodiedin various modified arrangementsuwithout departing from the invention.For instance a single but differentially Wound controlling generatormight be employed two generators C and D, with the field cxcitingcircuits 79 an 80 connected subthe combination of driving motors andmachines independently driven thereby proporhe operating speeds thereofa the respective driving motors, as clescribedw--- v 2. In a,-owe'r-transmission system of the rihscribecl the combination ofindethe-Hriving motors and'adapted to generate= currents of a valueproportionate to the rotary 8 code: of the motor armatures,

controlling lingcircuit,

y subthe potential values of sh t arranged to interpose resistance inthe field (Hi'fUliL of one of the driving motors, a

by the controldescribed. In a power transmission system of the cterescribed the combinatlonofi indeate currents of a .value proportionateto the rotary speeds of the motor armatures, connections betweentherespective generators to establish a dilferential therebetweenresponsive the respective generatorcircuits, a controlling rheosta-tarranged to interpose resistance-in the field circuit of one of thedriving motors, a controlling motor energized -b the controlling motorthe latter is operated responsive to the current of the controllingcircuit so as to adjust the field excitation of its associated-=mnintain a.

having their field magnets separately excited from the same circuit soas to have a circuit, operating connections from said conmotors, saidcontrolling motor and generatrolling motor to the rheostat whereby thetors having their field magnets separately latter is operated responsiveto the current excited from a common circuit to have a 10 of thecontrolling circuit so as to adjust the relatively constant value.

5 field excitation of its associated motor so as In testimony vvhereof Ihave signed my to maintain constant a predetermined ratio name to thisspecification. in the operating speeds of the respective HUGH NELSONHURD.

